A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs).
The desired pattern may be transferred onto the substrate by irradiating the substrate with a radiation beam from a projection system. The substrate is supported on and positioned relative to the projection system by a positioning stage. It is necessary correctly to align the substrate with the projection system in order that the desired pattern is applied at the correct location on the substrate. For this purpose the position in one or more degrees of freedom of the substrate relative to at least one optical element of the projection system is measured.
Movement of the positioning stage can lead to resonances in components used during measurement of the position of the substrate relative to the at least one optical element of the projection system. Such resonances result in stage positioning error which is an error in the position of the positioning stage due to an inaccurately measured position of the positioning stage relative to the at least one optical element of the projection system.
It is desirable to reduce stage positioning error.